"All three proposals had two features in common: They cut costs for students, and they gave us some short-term breathing room to take on bigger problems, including how to refinance $1 trillion in outstanding student loan debt and how to reduce the overall costs of college for all of our students. When we brought the last two proposals to a vote, they won by a majority, but they didn't pass because the Republicans filibustered both bills," Warren said. "We could have kept rates low, but the Republicans, every single one of them, voted to block that."

Majority Whip Richard J. Durbin came to the floor right after Warren and gave a peek at the way forward, which could include votes on amendments offered by Sens. Jack Reed, D-R.I., and Bernard Sanders, I-Vt. Neither of those would have enough support for adoption, and the Senate would then move to the compromise bill.

"Paying for college is tough and this legislation, I think, unfortunately could make it tougher because it would put in a permanent structure for setting student loan interest rates that could quickly result in students and parents paying more for student loans," Reed said in announcing his opposition to the compromise worked out by a bipartisan group of senators.

"This is not a temporary fix to get us to a better place in terms of incentives for tuition, in terms of refinancing, in terms of letting students more actively and more affordably pursue college education."

A few Democratic caucus members opposed the idea of a stopgap patch, however.

Durbin, an Illinois Democrat, said that he had recently spoken to President Barack Obama and that he knew the president planned to put forward a proposal dealing more broadly with college education costs.

Meetings to work out the bipartisan plan, which Durbin supports, took place in his leadership office on the third floor of the Capitol. He pushed his colleagues to take a realistic view and ultimately let the deal go forward.

"He doesn't like the choices we're faced with but he wants to keep interest rates below 6.8 percent, if we can. The bipartisan approach keeps them below 6.8 percent," Durbin said. "Voting against it means that students for the next four years will pay higher interest rates on their student loans than they have to. So I would encourage my colleagues, don't dismiss the bipartisan plan."

Some outside liberal groups, including the Progressive Change Campaign Committee, are joining in criticizing the compromise announced Wednesday night that is on track for Senate passage next week.

"The Senate proposal on student loans treats students like an ATM," PCCC co-founder Stephanie Taylor said in a statement. "Rates will go up to 8.25% for undergraduates and 9.5% for graduates under the deal — which is higher than if the Senate did nothing. Instead of pummeling students, Congress should listen to the more than 1,200 professors who support Sen. Warren's bill and lower rates for students."

Nonetheless, it is Durbin's job as Democratic whip to count the votes.

"There are some who want to hold out for something different. I'd like to join them, but I've watched the votes here. The senator from Massachusetts and I both voted the same way. We voted with Sen. Jack Reed, let's keep that rate at 3.4 percent, and we lost. Them he came back and said, wait a minute, let's try it again, and we lost. Now he's going to propose a 6.8 percent cap, which I can vote for, and we will lose again." Durbin said. "Then you face the reality. Are you going to say at that point, I don't want to talk about ... this anymore, I just want to go home, that's the end of the story? Students, pay 6.8 percent ... we couldn't solve it? Or do you accept this bipartisan compromise which brings the rates down for the next four years below 6.8 percent? I think that's a pretty easy choice."